Using the External Axial Extension
Contents
1. 0 0 om superior 0 0 om Normalization and Prescription Normalization Average of Prostate Normalization dose 100 Absolute dose 1 81 Gy 1 81 Gy Fraction comesponds to therelative dose 100 Fraction Information Beam number Y y4 S a Fraction Group Number Number of Fractions MU or min Fraction Nucletron Proprietary Information 555 00059CIB 00 Sy Nucletron NUC T125 02 Page 8 of 8 4 4 Remarks About the F5 Key Select Activity Structure Definition Select Flan F7 Target Definition E Cases i Image Registration volume Renderin Show SAC view 9 Show CC view Beam Modeling Plan Evaluation Show Current Case Toolbar l Dose Calculation Silent Calculation F5 Plan Optimization Brachy Planning Plan Analysis Export The F5 key allows the user to launch a silent dose calculation when it is unnecessary to modify the default dose calculation parameters dose calculation algorithm inhomogeneity correction In this case the Options dialog window of the Dose Calculation activity that includes the external extension values is not displayed and the calculation job is sent to the calculation queue If the default parameters have been modified by the user then the newly defined parameters will be used the next time the F5 key will be pressed This functionality has been introduced to improve the ergonomics and avoid too many mouse Clicks When a dose calculation is launched by2. using the F5 key the user must be sure that the default dose calculation parameters are clinically relevant for the patient case This recommendation also applies when a dose calculation is launched by clicking the dose module toolbar icon 5 Identification This bulletin concerns all versions of Oncentra MasterPlan and OTP 6 Consequences Without appropriate specification of the extension limits the dose distribution as well as the treatment time calculation may not be correct under estimation of the calculated dose regarding the expected dose and over dosage risk The magnitude of the potential over dosage is related to the ratio of the scattered dose to total dose which may vary depending on the treatment parameters energy field size position etc 7 Limitations amp Workarounds Always check that the external extension values are clinically relevant regarding the position and size of the beams of the plan This not only concerns the number of slices but also the position of the beams regarding the patient anatomical volume because a beam can on purpose or not be positioned at the edge of the patient 3D volume Keep in mind that for Oncentra MasterPlan by default the patient and thus the scattering volume is Strictly limited between the extreme slices Nucletron Proprietary Information 555 00059CIB 00
3. By Nucletro Improving patient care Customer Information Bulletin Title Using the External Axial Extension Scope All versions of Oncentra MasterPlan and OTP Target Group Users of Oncentra MasterPlan Dose Base Users of OTP Dose Base Nucletron Application Specialists Nucletron Proprietary Information 555 00059CIB 00 Sy Nucletron NUC T125 02 Page 2 of 8 Table Of Contents L DOCUMEN 6 See eee ee eee e ee Oa eK eee 2 2 Wocre Ti Vi css ca ce E E seeieaunecweceasseteaccees 2 3 FREIATOCR Documents scc E ER 2 A SUDOC E aa EA EAA E E E 2 4 1 Philosophy of 3D Dose Calculation in Oncentra MasterPlan ccccccccssssseeeeeeeeeeeeeees 2 4 2 Defining the Patient Volume Extension cccscscccccssseecseeeeecseseeecseseeeseageeessageeeseaseeeees 4 4 3 PRO WON eal AEA E na a a E E E E 6 4 4 Romake ADUCE I R SY srcceactha can cectaste veanstnitea ceanctineaacenasteeescladeacesyetemeecusketencuuesamesestosseaenes 8 Be TCSII AU aes cence sence ca setae see EE E A E cam cme A A A A E 8 COPS SOC SS ahi cst te iaa a tierce ee iaa a iaaa 8 7 Limitations amp Workarounds s snot 8 1 Document History Revision Who Reason for Change Changes oo LPN s S S SCSdYEPR237717 o O Not applicable o o 2 Where To Include Nucletron strongly advises you to insert this bulletin in any printed copy of the user manual 3 Related Documents Reference Revision Description 192 729ENG Oncentra Mas
4. al extension Inferior 0 ern SPE 0 cm roa Nucletron Proprietary Information 555 00059CIB 00 S Nucletron NUC T125 02 Page 6 of 8 4 3 Additional Remarks The external extension values can be defined in different places in Oncentra MasterPlan e Inthe Calculation Specification window of the Beam Modellng activity Dose presentation matris grid Fight 1858 cm Posterior Z 1489 cm Left 24 figg2 cm Anterior 22 hoe cm Res x jo5 om Res Z jo5 cri Points ss 7 Points Z Bz Default Grid Preview Interior r 0 70 cm Superior 0 70 cm Select all slices Select slices External axial extension Inferior fo cm Superior jo cm OF Cancel e Inthe Options window of the Dose Calculation activity Dose Calculation Options Otto Prostate Plan_and_dose Plani x Calculation specification Beam weighting Dose volume prescription Optimization conditions QA options l Optimize plan Number of fractions Radiation types Number of fractions fi Photon Becton Algorthm Dose Calculation Fluence Calculation f Pencil Beam i Classic Basis for density representation I Inhomogeneity comection Edemal ajal extension Collapsed Cone Enhanced Superior extension cm Inferior extension cm Dose presentation matris geometry Pixel spacing cm 7 00 x 7 00 Number of pixels per slice po x fp
5. e Oncentra MasterPlan treatment planning system the user has to define the dose presentation matrix dose points 3D grid in the Beam Modeling module before any dose calculation In the Tools menu select the Calculation Specification option The Calculation Specification window appears Dose presentation matris grid Fight 1858 crm Posterior Z 1489 cm Left 24 figs2 cm Anterior 2 hos cm Res x jo5 crm Res 4 jo5 crm Points s pe Points Z B Default Grid Preview Superior 0 70 cm Select slices Interior r 0 70 crm Select all slices External axial extension Inferior fo cm Superior fo cm OF Cancel Nucletron Proprietary Information 555 00059CIB 00 Sy Nucletron NUC T125 02 Page 5 of 8 By default this dose matrix encloses the anatomy contours of the patient in the X and Z directions in the axial plane However the calculation does not assume that the patient anatomy is infinite in the head feet direction Y ae ee eee ee ll a EEA ee Ee Ue A et ie PEE E a The External Axial Extension represents a patient volume extrapolation in order to obtain a better approximation of the scattered dose from the distant regions The system considers the extension shape to be identical to the shape in the inferior or superior slice The default superior and inferior extension values are set to 0 cm External axi
6. o Number of slices Shortest slice distance cm Nucletron Proprietary Information 555 00059CIB 00 Sy Nucletron Page 7 of 8 It can also be seen In the Approval window of the Plan Evaluation activity Approval i x Normalization Normalization Average of Prostate Normalization doze 100 Absolute dose 1 81 Gy comesponds to the relative dose 100 0 Dose matrix Resolution amp 1 00 cm 1 00 cm Number of points ps 2 40 39 30 External Axial Extension Inferior 0 00 cm superior 0 00 crn DRA parameters 1 E Beam number 4 5 Method Classic Classic Classic Classic Resolution 256 256 256 56 Sampled points FOS FOS AOS AOS Bone enhancement factor 12 0 12 0 12 0 12 0 Bone threshold 100 100 100 100 Min CT data threshold 1000 1000 1000 1000 Mas CT data threshold 3095 3095 3095 3095 Plan approved i In the Calculation Specification Details of the treatment protocol printout A Print Preview Zoom In 115 Zoom Out Print Patient Pros tate Otto name Patient ID Demo patient 2 N uc l et ron Birth date Se Case Plan_sand_dose Plan Plan Tri po Saved 29 Apr 2008 12 07 02 by Do tes tuser Printed 20 May 2008 18 17 15 by Of ts tuser Radiotherapie Dose Information Calculation Specification Details Matix res olution X 1 00 om Z 1 00 cm Matix dimensions X Zy 40 29 20 External axial extens ion inferior
7. s direction will be zero If there is not enough CT scanner information this may correspond to one single slice or a limited number of slices without sufficient extension one part of the beam will irradiate air instead of tissue and thus not generate any scattered dose So it is necessary to extend the volume in the direction of the missing scattering volume e g by 10 cm or 20 cm Dose presentation matris grid Fight a 5 58 cm Posterior Z a 469 om Left fi 8 92 cm Anterior 2 110 61 cm Res 4 jo cm Res Z Jo cm Poirits 3 76 Points 52 Default Grid Preview Inferior r 0 70 cm Superior r fa fall cm Select slices External axial extension Inferior 20 cm Superior jo cm Select all slices Nucletron Proprietary Information 555 00059CIB 00 ONG gt Nucletron NUC T125 02 Page 4 of 8 In the case of one single slice or a thin slab regarding the dimensions of the beam the extension has to be done in both directions towards head and feet by a sufficient value e g 20 cm Dose presentation matris grid Right 5 18 58 cm Posterior Z 1489 cm Lett 4 figse crm Anterior 2 foe crm Res s fos cm Res Z jos cm Points ss pe Points 2 sz Default Grid Preview Inferior r 0 70 cm Superior r o fall cm Select slices Select all slices al 4 2 Defining the Patient Volume Extension In th
8. terPlan User Manual Latest version available via the Nucletron Extranet 4 Subject As indicated in the sections of the user manual about beam modeling and plan evaluation the user is warned about the need to check that the volume extensions are clinically correct because otherwise the dose calculation could be incorrect After an issue was reported we have decided to inform you again about defining the volume extension of the patient before a dose calculation 4 1 Philosophy of 3D Dose Calculation in Oncentra MasterPlan Oncentra MasterPlan is a 3D treatment planning system that calculates dose based on volumetric information represented by the patient anatomy This anatomy generally acquired from CT scanner slices is usually limited to the treatment region During dose calculation due to the 3D nature of the algorithms the scattered component coming from the surrounding volume is contributing to the dose in all calculation grid points and simulates as best as possible the physical mechanism of dose deposition Nucletron Proprietary Information 555 00059CIB 00 Sy Nucletron NUC T125 02 Page 3 of 8 For this reason and to properly take into account the scattered dose the patient 3D volume and thus the total number of CT slices must extend far beyond the beam dimensions Unless of course if there is no real anatomical information in a direction as for the top of the head In this case the extension in thi
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